My year with a battery - A year of savings.

JSHarris

Interesting thread.  We've had a 21kWh battery system for a bit over two years now.  Some of the benefits were hidden when I did the initial sums (before the energy crisis).  Biggest single benefit was the way that having a battery system massively improved the effectiveness of charging the car from solar.  I'd really not realised just how much of a difference this made.

The reason it works so well is because the house battery acts as a buffer.  This means I can charge the car more effectively on a day when the sun is going in and out behind clouds.  When clouds cause the PV output to dip the battery makes up the difference.  When the sun pops out again the house battery gets topped back up.  I have the charge point set to drop to the minimum the car will accept (6A, about 1.4kW) when the PV output drops away, with the advertised current rising as the PV output increases, but always leaving a margin to allow the house battery to top up.

Last year (2022) we used 54kWh of peak rate electricity (our house is all-electric, electric heating, hot water, cooking etc).  That includes charging the car.  We used 4,103kWh of off-peak electricity.  Overall I don't think that's too bad for a 130m² house, especially as we keep the house at around 21°C to 22°C all year around, and don't really economise on anything.

Not sure what the payback on the battery system will be, as I originally installed it as a way to provide a backup during power cuts.  Between 2018 and 2020 we had 27 power cuts, varying from an hour or two to a bit over a day.  I was going to get a generator, in fact I installed a generator changeover switch and borrowed one for a time, but then realised that a battery system wouldn't make the unholy row that the generator created.

michaels

JSHarris said:

Interesting thread.  We've had a 21kWh battery system for a bit over two years now.  Some of the benefits were hidden when I did the initial sums (before the energy crisis).  Biggest single benefit was the way that having a battery system massively improved the effectiveness of charging the car from solar.  I'd really not realised just how much of a difference this made.

The reason it works so well is because the house battery acts as a buffer.  This means I can charge the car more effectively on a day when the sun is going in and out behind clouds.  When clouds cause the PV output to dip the battery makes up the difference.  When the sun pops out again the house battery gets topped back up.  I have the charge point set to drop to the minimum the car will accept (6A, about 1.4kW) when the PV output drops away, with the advertised current rising as the PV output increases, but always leaving a margin to allow the house battery to top up.

Last year (2022) we used 54kWh of peak rate electricity (our house is all-electric, electric heating, hot water, cooking etc).  That includes charging the car.  We used 4,103kWh of off-peak electricity.  Overall I don't think that's too bad for a 130m² house, especially as we keep the house at around 21°C to 22°C all year around, and don't really economise on anything.

Not sure what the payback on the battery system will be, as I originally installed it as a way to provide a backup during power cuts.  Between 2018 and 2020 we had 27 power cuts, varying from an hour or two to a bit over a day.  I was going to get a generator, in fact I installed a generator changeover switch and borrowed one for a time, but then realised that a battery system wouldn't make the unholy row that the generator created.

Haha  We use about 15,000kwh per year and all that heats is half the hot water.

JSHarris

michaels said:

JSHarris said:

Interesting thread.  We've had a 21kWh battery system for a bit over two years now.  Some of the benefits were hidden when I did the initial sums (before the energy crisis).  Biggest single benefit was the way that having a battery system massively improved the effectiveness of charging the car from solar.  I'd really not realised just how much of a difference this made.

The reason it works so well is because the house battery acts as a buffer.  This means I can charge the car more effectively on a day when the sun is going in and out behind clouds.  When clouds cause the PV output to dip the battery makes up the difference.  When the sun pops out again the house battery gets topped back up.  I have the charge point set to drop to the minimum the car will accept (6A, about 1.4kW) when the PV output drops away, with the advertised current rising as the PV output increases, but always leaving a margin to allow the house battery to top up.

Last year (2022) we used 54kWh of peak rate electricity (our house is all-electric, electric heating, hot water, cooking etc).  That includes charging the car.  We used 4,103kWh of off-peak electricity.  Overall I don't think that's too bad for a 130m² house, especially as we keep the house at around 21°C to 22°C all year around, and don't really economise on anything.

Not sure what the payback on the battery system will be, as I originally installed it as a way to provide a backup during power cuts.  Between 2018 and 2020 we had 27 power cuts, varying from an hour or two to a bit over a day.  I was going to get a generator, in fact I installed a generator changeover switch and borrowed one for a time, but then realised that a battery system wouldn't make the unholy row that the generator created.

Haha  We use about 15,000kwh per year and all that heats is half the hot water.

Bloody hell!  That would run everything in our house and run the car for well over 3 years!  Our hot water usage is around 3.5kWh to 4.5kWh per day, but for a fair bit of the year the PV system charges the hot water up, so there's no grid electricity usage.  We've been "off grid" since 12th may this year, all our energy has come from the PV system.  I doubt we'll need to use any grid power until some time around the end of September.

mmmmikey

EricMears said:

I don't think you can use a smart meter to record exports unless you have an 'export MPAN'.  And surely only you (or your import supplier ?)  can apply for that.  

Hi - I was on metered export with EDF (for FIT payments) with a smart meter without an export MPAN. It worked by providing EDF with readings from the smart meter at the same time as submitting the generation readings. I've just switched to Octopus for the export which involved getting an export MPAN - an easy enough process that was sorted in a day or so.

pensionpawn

Metered export today = £9.41. Profit of £14.63 after generation FiT, import & s/c (no battery). Do the sums on metered export, it could work for you too.

QrizB

pensionpawn said:

Metered export today = £9.41. Profit of £14.63 after generation FiT, import & s/c (no battery). Do the sums on metered export, it could work for you too.

I'm generating 2700kWh a year, exporting 900 and importing 1500. I don't think the 600 net import will be cheaper on Flux than it is on Go. It's not even worth switching to Octopus's SEG rate for export since 1350 * 4.82 is more than 900 * 4.1.

OTOH my FIT generation payments for the year should be about £1800, which will be nice

mmmmikey

It quickly gets complex - best for me by far at the moment is Octopus Agile for import and Octopus Outgoing Fixed for export which pays me 15p/kWh for export, more than twice what I was getting for export previously. It also changes the economics of other things - it now becomes better for me to use bottled gas for water heating because the additional income from increased export outweighs the cost of the gas. Unless the Agile rate falls the less than about 12p/kWh in which case it's better to import the electricity and save the money on gas. And so it goes on - work on smart controls to automate this is ongoing

ispookie666

I'm a bit skeptical about energy arbitrage.
I'm more than happy to be self sufficient, reduce the grid draw and if I have excess, then export.  

JSHarris

ispookie666 said:

I'm a bit skeptical about energy arbitrage.
I'm more than happy to be self sufficient, reduce the grid draw and if I have excess, then export.  

I agree with you.  I've never been convinced by it at the domestic level.  It works very, very well at the generator level, arguably too well, as some generators deliberately ransom the grid to ensure they maximise their income (not saying this is against the rules - it's not).  At the moment we have generators collectively refusing to supply, and  by doing so they push the spot market prices up.  when these prices are high enough they decide to sell electricity at a price way above cost.

About a year ago I was at a meeting with an operator of a fairly local (and new) battery storage facility.  The meeting was a pitch to investors for future expansion and included an open admission that engineering best arbitrage conditions was key to their projected income.  From an investor perspective this seemed fine.  From a moral perspective (coming from a view that energy supplies are essential to life now) I wasn't at all comfortable.

michaels

JSHarris said:

ispookie666 said:

I'm a bit skeptical about energy arbitrage.
I'm more than happy to be self sufficient, reduce the grid draw and if I have excess, then export.  

I agree with you.  I've never been convinced by it at the domestic level.  It works very, very well at the generator level, arguably too well, as some generators deliberately ransom the grid to ensure they maximise their income (not saying this is against the rules - it's not).  At the moment we have generators collectively refusing to supply, and  by doing so they push the spot market prices up.  when these prices are high enough they decide to sell electricity at a price way above cost.

About a year ago I was at a meeting with an operator of a fairly local (and new) battery storage facility.  The meeting was a pitch to investors for future expansion and included an open admission that engineering best arbitrage conditions was key to their projected income.  From an investor perspective this seemed fine.  From a moral perspective (coming from a view that energy supplies are essential to life now) I wasn't at all comfortable.

Doesn't that sort of market manipulation mean there should be lots of value available for an aggregator who was able to deliver negawatts via bundling demand shaping and domestic battery export?  This can also in theory be delivered at the micro level to where ever on the grid is experiencing shortages.